From the web site:
"After the insects, mites (the subclass of the Arachnida named Acari or Acarina) are the most diverse and difficult group of arthropods encountered in quarantine. Like insects, but unlike their arachnid relatives (spiders, scorpions and the like), the feeding ecologies of mites go well beyond predation to include herbivory and parasitism. The Acari includes a host of plant parasites that can devastate crops by their feeding or by transmitting plant pathogens. Domestic and wild animals also are infested by an often bewildering diversity of parasitic mites, including those that cause debilitating disease and deformity. Even other arthropods are not immune, as the worldwide spread of the honeybee parasite varroa has demonstrated. Social insects and those that bore in timber are especially rich in associated mites – and for most of these mites we have no idea what their potential impact may be if they are introduced into new areas.

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